Browsing by Subject "cytotoxic T cells"

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    Receptor-Mediated Antigen Delivery by Α2-Macroglobulin: Effect on Cytotoxic T Lymphocyte Immunity and Implications for Vaccine Development
    (2009) Bowers, Edith Villette

    The receptor-recognized form of α2-macroglobulin (α2M*) targets antigens (Ag) to professional Ag-presenting cells (APCs) for rapid internalization, processing, and presentation. When employed as an Ag delivery vehicle, α2M* amplifies major histocompatibility complex (MHC) class II presentation as demonstrated by increased antibody (Ab) titers. Recent evidence, however, suggests that α2M*-encapsulation may also enhance Ag-specific cytotoxic T lymphocyte (CTL) immunity. In these studies, we demonstrate that α2M*-delivered Ag (ovalbumin, OVA) enhances the production of specific in vitro and in vivo CTL responses.

    Murine splenocytes expressing a transgenic T cell receptor (TCR) specific for CTL peptide OVA257-264 (SIINFEKL) demonstrated up to 25-fold greater IFN-γ and IL-2 secretion when treated in vitro with α2M*-OVA compared to soluble OVA. The frequency of IFN-γ -producing cells was increased ~15-fold as measured by ELISPOT. Expansion of the OVA-specific CD8+ T cells, as assayed by tetramer binding and [3H]thymidine incorporation, and cell-mediated cytotoxicity, as determined by a flow cytometric assay, were also significantly enhanced by α2M*-OVA. Furthermore, CTL responses were observed at Ag doses tenfold lower than those required with OVA alone.

    We also observed enhanced humoral and CTL responses by naïve mice following intradermal immunization with α2M*-OVA. These α2M*-OVA-immunized mice displayed increased protection against a subcutaneously implanted OVA-expressing tumor, as demonstrated by delayed tumor growth and prolonged animal survival. The anti-tumor response observed with α2M*-mediated Ag delivery was comparable to that of an accepted vaccine adjuvant (CpG 1826) and appeared superior to a cell-based vaccine technique.

    To further understand the mechanism underlying this enhanced CTL immunity, the subsets of professional APCs capable of cross-presenting α2M*-encapsulated Ag were investigated. Although both dendritic cells (DCs) and macrophages appear to stimulate some degree of cross-priming in response to α2M*-encapsulated Ag, CD8+CD4- and CD8-CD4+ DCs appear to do so with the greatest efficiency. The implications of this finding to the ongoing debate regarding the relative contributions of APC subsets to Ag cross-presentation and the determinants of which cells cross-present with high efficiency are discussed.

    These observations demonstrate that α2M*-mediated Ag delivery promotes cross-presentation resulting in enhanced Ag-specific CTL immunity. Considered in the context of previous work, these results support α2M* as an effective Ag delivery system that may be particularly useful for vaccines based on weakly immunogenic subunits or requiring dose sparing.

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    Redirection of Cord Blood T Cells and Natural Killer Cells for Elimination of Autologous HIV-1-Infected Target Cells Using Bispecific DART® Molecules.
    (Frontiers in immunology, 2020-01) Pollara, Justin; Edwards, R Whitney; Jha, Shalini; Lam, Chia-Ying Kao; Liu, Liqin; Diedrich, Gundo; Nordstrom, Jeffrey L; Huffman, Tori; Pickeral, Joy A; Denny, Thomas N; Permar, Sallie R; Ferrari, Guido
    Mother-to-child transmission of HIV-1 remains a major global health challenge. Currently, HIV-1-infected infants require strict lifelong adherence to antiretroviral therapy to prevent replication of virus from reservoirs of infected cells, and to halt progression of disease. There is a critical need for immune interventions that can be deployed shortly after infection to eliminate HIV-1-infected cells in order to promote long-term remission of viremia, or to potentially cure pediatric HIV-1-infection. Bispecific HIV × CD3 DART® molecules able to co-engage the HIV-1 envelope protein on the surface of infected cells and CD3 on cytolytic T cells have been previously shown to eliminate HIV-1 infected cells in vitro and are candidates for passive immunotherapy to reduce the virus reservoir. However, their potential utility as therapy for infant HIV-1 infection is unclear as the ability of these novel antibody-based molecules to work in concert with cells of the infant immune system had not been assessed. Here, we use human umbilical cord blood as a model of the naïve neonatal immune system to evaluate the ability of HIV x CD3 DART molecules to recruit and redirect neonatal effector cells for elimination of autologous CD4+ T cells infected with HIV-1 encoding an envelope gene sequenced from a mother-to-child transmission event. We found that HIV × CD3 DART molecules can redirect T cells present in cord blood for elimination of HIV-infected CD4+ T cells. However, we observed reduced killing by T cells isolated from cord blood when compared to cells isolated from adult peripheral blood-likely due to the absence of the memory and effector CD8+ T cells that are most cytolytic when redirected by bispecific DART molecules. We also found that newly developed HIV × CD16 DART molecules were able to recruit CD16-expressing natural killer cells from cord blood to eliminate HIV-infected cells, and the activity of cord blood natural killer cells could be substantially increased by priming with IL-15. Our results support continued development of HIV-specific DART molecules using relevant preclinical animal models to optimize strategies for effective use of this immune therapy to reduce HIV-1 infection in pediatric populations.